<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="./src/react.js"></script>
    <script src="./src/react-dom.js"></script>
    <script src="./src/babel.js"></script>
</head>

<body>
    <div id="app"></div>
</body>
<script type="text/babel">
 class Biaodan extends React.Component{
        constructor(){
            super();
           this.user=React.createRef()
        }
        add=()=>{
           
            // 第一种方法通过获取id来获取输入框的值
            console.log(document.getElementById('username').value);

            // 第二种方法通过ref来获取
            console.log(this.user.current.value)
        }
        render(){
       
            return (
            <div>   
               <input type="text" defaultValue='aaa' id='username' ref={this.user} />
               <input type="button" value='提交' onClick={this.add} />
            </div>
            )
        }
     }
    ReactDOM.render(
            <div>
                <Biaodan></Biaodan>
            </div>,
            document.getElementById("app")
        )
        
    </script>

</html>